1. Field of the Invention
This invention relates to a device which is primarily of interest in the field of lighting for such applications as photography, television and video as well as general home and office use.
More pleasant and less harsh lighting effects are invariably obtained by employing light sources of large size rather than of small size. It is consequently a very common practice to employ light-diffusion boxes in order to convert the original small-size light source to one of larger size. The present invention offers an improved device for the achievement of this objective.
2. Description of the Prior Art
Many different types of light-diffusion boxes are already known and include the following:
(1) boxes which are made of light-reflecting material stretched out and held in shape by means of a metal framework. These light-diffusion boxes have an advantage in that they are completely collapsible and of very light weight. However, they are relatively high in capital cost by reason of the considerable labor involved in manufacture both of the fabric or plastic cover and of the metal parts. They also have an unattractive appearance and suffer from the limitations imposed by their basically pyramidal shape. They have no rigidity and the fabric cover is easily damaged by the metal parts. In addition, the light-transmitting face is always flat.
(2) Light-diffusion boxes made up of components similar to those mentioned in the foregoing paragraph but having a basically semi cylindrical shape are also well-known. However, they suffer from all of the same defects and always have a flat front face.
(3) Rigid non-collapsable light-diffusion boxes of various concave shapes which are fabricated from different plastics or aluminum alloys and are molded or shaped by various means. Tooling costs are thus very high. Although the boxes may be nested together for mass shipment, their volume and weight still remain exorbitantly high for individual shipment and costly packages of large size are necessary. These molded light-diffusion boxes are usually flat-faced. Although some types can be fitted with a molded three-dimensional front face, this face permanently retains its three-dimensional character. The interior of a diffusion box of this type is usually painted white or in a natural aluminum color but this is also a costly procedure and fails to achieve the desirable standard of efficiency.
(4) Another existing type of light-diffusion box essentially having a triangular or pylon shape with prismatic facets and thus provided with a three-dimensional light-emitting face as well as a three-dimensional rear portion. These boxes have the disadvantage in that the light source must either be incorporated in the box or else attached at one or both of its two open ends. Furthermore, if these diffusion boxes are provided with prismatic and opaque light-reflecting rear walls, they become very complicated to assemble and costly to manufacture by reason of the large number of parts to be made. A further disadvantage of a box of this type is that its light-transmitting face always remains three-dimensional. The reflection produced by a face having this shape may occasionally prove objectionable by reason of the fact that it is not rectangular. Since the shape of the light-diffusion box as a whole is usually oblong, it would often be useful to place it in any desired position between a vertical plane and a horizontal plane. However, this cannot be achieved simply by pivotal displacement of the box about its center since no provision is made for any pivotal support or central holding point. A further drawback is that it is necessary in the case of boxes of greater length to provide two light sources each mounted at one end in order to ensure uniform illumination over the entire length of the light-diffusion box.
(5) Prismatic three-dimensional front-faced light-diffusion boxes of existing types having a flat-faced and metallized opaque rear wall fabricated from a cut and embossed plastic sheet. These boxes have many advantages over the types mentioned above in paragraphs 1, 2 and 3. However, they suffer from the fact that their front face always remains in three-dimensional form, which incurs a certain loss of light along the axis illuminated by the box. At certain times, there may also be objectionable reflections from the non-rectangular front face of the box. In addition, the flat surface of the rear wall is attended by two further drawbacks. In the first place, this flat wall confers little strength and rigidity on the box. Secondly, homogeneous light-mixing is not achieved since the internal reflecting surface is flat.